This invention relates to a housing for an electronic component such as a signal transformer.
Electronic components are often mounted in housings before being assembled with other components on a circuit board. Usually the space between the component and the internal walls of the housing (and any internal space within the component) is filled with a resin to encapsulate the component. Mounting the component within a housing ensures that the component is electrically isolated from adjacent components on the circuit board, protects the component from damage and eases handling and assembly of the component.
According to the invention, there is provided a housing for an electronic component, the housing having a set of walls for surrounding the component, an open base through which the component can be introduced into the housing and through which component terminals can be exposed to allow the component to be mounted on a circuit board, snap-fit features past which the component can snap to retain the component in the housing and internal springs which, in use, bias the component into contact with the snap-fit features.
This type of construction has many benefits when compared with the conventional xe2x80x98pottingxe2x80x99 or xe2x80x98encapsulationxe2x80x99 processes. Assembly of the component into the housing now requires only one mechanical action and can provide electrical insulation and isolation for the component. Because there is no encapsulating compound surrounding the component, disassembly and recycling of the materials from which the component is made is easily possible.
The housing is preferably parallelepipedic in form and has five walls, an open face through which the component can be introduced, and openings at or near the apexes of the housing. This is the conventional shape for component housings and allows them to be easily handled and oriented.
The snap-fit features may comprise a set of resilient lugs moulded as part of the housing and past which the component can snap to hold the component in the housing. Alternatively, the housing can have a set of apertures or recesses into which features on the component can locate with a snap-fit action.
Furthermore, the internal springs which, in use, bias the component into contact with the snap-fit features prevent any rattling or looseness. The housing can be of moulded plastics with the springs moulded as integral parts of the housing.
The housing preferably has side walls, and at least part of the lower edge of at least part of the side walls is cut-away relative to at least other parts of the side walls, so that the parts which are not cut-away form feet which contact a substrate when the housing is in use and the cut away parts allow a fluid flow path into and out of the housing. The housing may also have apertures in its walls to allow a fluid flow path into and out of the housing. These apertures can be at the corners of a parallelepipedic housing.
The top wall of the housing is preferably flat and can serve as a surface for carrying a manufacturer""s mark and/or as a surface which can be contacted by vacuum handling equipment.
The invention extends to the combination of an electronic component and a housing therefor, the housing having a set of walls for surrounding the component, an open base through which the component can be introduced into the housing, both the housing and the component having snap-fit features with the snap-fit features of the housing and of the component being arranged to be snap-fitted together to retain the component in the housing so that component terminals are exposed through the open base to allow the component to be mounted on a circuit board, the housing having internal springs which, in use, bias the snap-fit features into contact to prevent play between the component and the housing.
The component can be a transformer with a housing, a bobbin, coils wound on the bobbin and core laminations fitted on the bobbin. The bobbin includes snap-fit features adapted to engage with snap-fit features in the housing, and the housing includes integral springs which press the laminations against one another in a stack when the transformer is fitted in the housing and bias the bobbin into contact with the snap-fit features.
In this case, the size and position of the openings through the housing walls is such as not to compromise the required creepage and clearance requirements and the thickness of the housing walls is sufficient to meet the solid insulation requirements of the transformer.
The transformer laminations will be stacked one on the other in the bobbin and the springs in the housing will press the laminations against one another to ensure good magnetic performance, with the spring force being transmitted through the laminations to the bobbin to press the snap-fit features on the bobbin against the snap-fit features in the housing. The laminations are not directly secured together or to the bobbin, but are prevented from being displaced after assembly by the proximity of the walls of the housing.
According to another aspect of the invention, there is provided a transformer having a housing, a bobbin, coils wound on the bobbin and core laminations fitted within the bobbin, wherein the bobbin is a plastics moulding which includes snap-fit features adapted to engage with snap-fit features in the housing, and the housing includes integral springs which press the laminations against one another in a stack when the transformer is fitted in the housing.
When the component is a transformer as described here, there are significant recycling advantages. The plastics housing can be detached to remove the transformer. The laminations can be extracted, as they are only held in position by the housing, and the copper wire can be unwound from the bobbin. The plastics bobbin and housing can be recycled using conventional plastics recycling techniques (and it does not matter if the snap-fit features are damaged during disassembly, as recycling will normally involve remelting the plastics); the copper wire can be recycled after remelting and the laminations can be reused without any further treatment. The material of the laminations is expensive, and this recycling can be worthwhile if only to recover and reuse the laminations. None of this would be feasible with an encapsulated or varnish impregnated component which would have to be disposed of in landfill.